JPS6424159A - Fuel injection device for engine - Google Patents

Abstract

PURPOSE:To promptly decrease a pressure of fuel in a fuel chamber and to improve a cut of fuel prevented from its after drip by providing a pressure switching means wherein the fuel chamber in a fuel injection valve communicates with a low pressure source when the pressure of fuel decreases in the final period of fuel injection. CONSTITUTION:Delivered fuel from a fuel injection pump 31 is introduced to a pressure chamber 10 in a pressure source switching means 20, provided in a fuel injection valve 1, through a delivery valve 32. And moving a piston 21 to the left, the fuel, which is supplied into a fuel chamber 3 passing through a high pressure oil path 11, is injected by lifting a needle valve 2. On the contrary, in the final period of fuel injection, a pressure of fuel in the high pressure oil path 11 decreases while the delivery valve 32 closes. Here moving the piston 21 to the right, the fuel chamber 3 communicates with an oil tank 30, serving as the low pressure source, through the high pressure oil path 11 and a return oil path 12. By the constitution thus obtained, the needle valve 2 is rapidly closed by promptly decreasing the pressure of fuel in the fuel chamber 3.